This invention relates to pallets, and in particular to inexpensive and lightweight pallets.
The pallets of the present invention preferably are constructed of corrugated cardboard, however, it will be appreciated that they may be constructed of other similar types of materials such as solid fibreboard or pasted chipboard.
Prior art pallets have employed flat corrugated pallet decks to which a plurality of leg members are attached. The pallet deck is supported above its resting surface so that the pallet and its contents may be picked up by mechanized equipment such as a forklift truck.
Prior art corrugated pallets have utilized a simple and effective attachment means by which a tubular cardboard leg, usually constructed of spiral laminated paperboard material, is attached to the pallet deck by gluing. To effect a strong attachment, the prior art corrugated pallets have utilized a sunburst-shaped pattern which is die-cut in the corrugated pallet deck at each leg attachment point. The die-cut pattern utilizes a central hole with radiating die cuts terminating at an outer radius corresponding to the inner diameter of the pallet leg. The finger members thus formed are generally referred to as straight finger members and have blunt tips where they originate from the central hole.
After cutting, the straight finger members are forced downward into an annulus between two nested tubular leg elements. Glue is applied to the finger elements prior to being forced downward into the annulus to fixedly secure the finger elements within the annulus, and hence the pallet leg to the pallet deck. Pallets having pallet legs attached thereto in the manner described are disclosed in U.S. Pat. Nos. 2,665,807; 3,052,397; 3,266,444 and French Pat. No. 1,470,774.
An improvement of the above-described pallet and method of attaching pallet legs thereto is disclosed in U.S. patent application Ser. No. 453,760, filed Dec. 27, 1982. As disclosed therein, the finger elements are formed by die-cut lines tangent to a central hole so that a somewhat spiral pattern is formed, much like a camera iris. The resulting finger members are generally referred to as spiral finger elements, as opposed to the straight finger elements. These spiral finger elements, according to various test results, provide a pallet leg which is far stronger and less subject to damage when a sideways force parallel to the pallet deck member is applied to the pallet leg.
The pallets disclosed in the above-identified U.S. patents and the referenced patent application, in many cases, have another corrugated cardboard pallet deck member adhesively affixed atop the pallet deck to which the pallet legs are affixed in order to provide additional strength to the pallet. The pallet per se is strengthened in this fashion, but the added pallet deck member does not strengthen to any substantial degree the pallet leg against damage from sideway forces applied to them.
While the pallets of the above-identified type are generally satisfactory, there is still a desire for an inexpensive and lightweight pallet of corrugated cardboard which has both greater deck strength and pallet legs which are not as susceptible to damage when a sideways force is applied to them. The deck strength can be increased by adhesively affixing another pallet deck member atop the pallet deck as described above, but this method of increasing the deck strength suffers from the expense and difficulties associated with adhesively affixing the other pallet deck member to the pallet. For example, adhesive must be applied to one or surfaces of the two pallet deck members, the two deck members properly aligned atop one another, and then clamped until the adhesive sets. These requirements all add to the cost of the pallets.
Also, for the purpose of storing and shipping these standard pallets, the pallets normally are stacked atop one another to a height of 84". The four corners of the stacked pallets are protected with creased corrugated cardboard dimensioned to extend the 84" height of the stack and 6 inches on each side of the stack about the corners. The stacked pallets then are stretch wrapped or banded. The need to provide the corner protectors likewise adds to the cost of the pallets.
Accordingly, it is an object of the present invention to overcome the above as well as other disadvantages of these prior art pallet designs, and to provide an improved inexpensive and lightweight pallet having both a greater deck strength and pallet legs having greater strength against sideways force applied to them.
Further still, it is an object to provide such an improved pallet which is far simpler to manufacture.
A still further object is to provide such an improved pallet which is far simpler and less expensive to stack for storage and shipment.
The above as well as other objects not specifically mentioned are accomplished by providing a pallet having a pallet deck which is formed from at least two pallet deck members, each of which has finger elements die-cut therein at each leg attachment point. The pallet deck members may be of solid fibreboard, pasted chipboard and other like materials, however, it is preferred to use corrugated cardboard since this material is lightweight and the most expensive. The pallet legs are formed from tubular outer and inner leg elements, and are attached to both pallet deck members by stacking them atop one another and forcibly urging the finger elements on both pallet deck members within the annulus between the nested outer and inner leg elements. With this construction, the pallet deck is increased in strength since two pallet deck members are utilized and the pallet legs have greater strength and are less subject to damage from sideways forces parallel to the pallet applied to them since they are attached to the pallet by the finger elements die-cut in both of the pallet deck members.
Pallets constructed in this fashion also are far easier to assemble. The finger elements are die-cut into each of the pallet deck members by the same die, and therefore are in perfect alignment when the two deck members are stacked atop one another. Also, it is not necessary to adhesively affix the two deck members to one another, since the tubular leg elements effectively function like rivets to secure the deck members together. Preferably, however, some adhesive is applied to the mating surfaces of the deck members. Even though some adhesive is used, a substantial advantage is still provided, since the tubular leg elements function to secure the deck members together until the adhesive sets, thus the need to clamp them together as in the past is eliminated.
A multiple number of pallet deck members can be stacked atop one another to form the pallet deck and when corrugated cardboard is used each pallet deck member can be single wall, double wall or thicker corrugated cardboard or any combination thereof. However, in a preferred embodiment, only two pallet deck members are used, and each of them is a double wall corrugated cardboard. The double wall deck members are die-cut and assembled as described above, and provide a pallet which is both economical and sufficiently strong for most applications. The inner leg elements preferably are of a length to substantially cover the finger elements when assembled to form the pallet legs. The pallet legs can be reinforced for both load capacity and abrasive wear by using an inner leg element which is of substantially the same height, or length, as the outer leg element. A pallet leg of this construction also can be used on a standard pallet which has a pallet deck formed on one single wall corrugated cardboard deck member, but the single wall corrugated deck member does not have sufficient strength and the pallet leg under extremely rough use can be torn off. Accordingly, there is little benefit in reinforcing the pallet legs on a standard pallet in this fashion, if the pallet is to be subjected to extremely rough use.
In accordance with the invention, it is also preferred to cross laminate the corrugated cardboard deck members, i.e., the corrugations of the deck members extend perpendicular to each other. Such cross laminating of the deck members substantially increases the deck strength of the pallet. Further still, according to the invention, a substantial improvement in the strength of the pallet legs is provided whether straight or spiral finger elements are used, when the finger elements die-cut in both pallet deck members are captured between the nested outer and inner legs elements. Again, however, it is preferred to use spiral finger elements, since they provide several advantages not provided by the straight finger elements. In particular, the spiral finger elements are much stronger and therefore provide a pallet leg which is much stronger and more resistant to sideways forces applied to them. In addition, the spiral fingers are longer in length than the straight fingers. Accordingly, when the multiple corrugated cardboard deck members are used, the spiral finger elements when forced downwardly into the annulus between the two nested outer and inner leg elements forming the pallet legs provide a longer and hence more finger surface area which is affixed together to one another and to the walls of the leg elements.
Also, according to the invention, it is preferred that the spiral finger elements on each of the pallet deck members substantially fully overlap each other. Also, the score lines defining the outer periphery of the finger elements should project downwardly on both pallet deck members when stacked atop one another. In order to achieve this arrangement, one pallet deck member is run through the die-cutting machine with its corrugations running in one direction and the other pallet deck member is run through with its corrugations running perpendicular to the first deck member. Effectively, a top and a bottom pallet deck member are die cut, but it makes no difference which is the top, or the bottom, deck member. When die-cut in this fashion and stacked atop one another with a cross lamination, the finger elements when forced downwardly into the annulus between the nested outer and inner leg elements will substantially fully overlap each other. The overlapped spiral finger elements provide pallet legs which have far greater strength, particularly against sideways forces applied against them.
It is also possible to die-cut the pallet deck members as described above, and to then flip over one pallet deck member and stack it atop the other. In this instance, however, when the finger elements are forced downwardly into the annulus between the outer and inner leg elements, the spiral finger elements of one deck member project radially in one direction and those on the other deck member project radially in the opposite direction so that there is a radial overlapping of the finger elements. While assembling the pallet deck members in this fashion provides an increase in the strength of the pallet legs, the increase is not as great as it is when the finger elements substantially fully overlap each other.
Pallets constructed in accordance with the present invention provide still another advantage over the standard pallets when stacking the pallets for storage or shipment. As indicated above, the pallets normally are stacked atop one another to a height of 84" and prior to handling or stretch wrapping the stacked pallets, the four corners of the stacked pallets are protected with corrugated cardboard corner protectors. Since the deck members of the pallets of the present invention are much stronger than the standard pallets, it is found that the normally used corrugated cardboard corner protectors can be eliminated. Also, the pallets can be secured in the stacked relationship simply by banding them together by extending a band through the holes of the pallet legs. In each instance, a substantial cost savings is provided.
A lightweight and inexpensive pallet having exceptional beam strength for supporting and transporting heavy loads, by means of forklift trucks and automated mechanical load handling conveying or transporting equipment, can be provided by adding a second pallet deck to the underside of the pallet. More specifically, according to the invention, a second pallet deck is secured to the pallet by attaching the second pallet deck to the bottom of the pallet legs in the same fashion as the pallet deck is attached to the top of the pallet legs. The pallet legs thus are effectively sandwiched between the two pallet decks. With this construction, a rigid pallet having a substantially greater beam strength, i.e., less tendency to flex in the longitudinal plane thereof, is provided. The beam strength also can be increased by affixing parallel strips, as opposed to a fully pallet deck, to the pallet legs. Further still, the beam strength can be increased by extending one length of the pallet deck such that the pallet deck can be folded essentially U-shaped along two opposing edges thereof and affixed to the pallet legs.
Other objects and advantages of the invention will become apparent from the following detailed description and upon reference to the drawings.